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## Heavy Ion Physics from RHIC to LHC

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**Heavy Ion Physics from RHIC to LHC**Joe Kapusta University of Minnesota University of Seoul 19 April 2008**Bevatron + SuperHILAC = Bevalac**Purpose: Create dense nuclear matter in the laboratory for a brief moment. • 1974-75: Beams of carbon and oxygen accelerated to 2.1 GeV/nucleon. • 1981-82: Upgraded to accelerate beams up to uranium at 1 GeV/nucleon. • 1993: Turned off for the last time, being eclipsed by the higher energies • available at the AGS at BNL and at the SPS at CERN.**Lattice Gauge Theory w/o Dynamical Quarks**Heavy quarks are deconfined beyond the transition temperature Equation of state exhibits first order phase transition Calculations by Bielefeld group.**For realistic quark masses**there may be a line of 1st order transition terminating at a critical point. de Forcrand, Philipsen The phase transition is 2nd order for 2 massless flavors and 1st order for 3, otherwise a rapid crossover. Karsch, Laermann, Peikert**Colliding beams**of 100 GeV/nucleon gold nuclei to create quark-gluon plasma.**How does RHIC connect to other fields like cosmology and**condensed matter physics?**Pictorial of a Heavy Ion Collision**Hard parton scattering & jets Strong classical fields Quark-Gluon Plasma Hydrodynamic flow Hadronic rescattering Hadronization Time < 1fm/c ~ 10 fm/c**Au+Au Collisions**Thousands of particles created! RIKEN/BNL Research Center**Are collisions at RHIC**just superpositions of nucleon-nucleon collsions?**Are collisions at RHIC**just superpositions of nucleon-nucleon collsions? Absolutely not!**Temperature**• Hadron ratios:**Compilation of freezeout conditions**from the SIS, AGS, SPS and RHIC.**q**q Hard Probes • Use hard processes as plasma probes • hard processes jet production, photons, etc. • Calibration under control • perturbative calculations • p+p baseline experiment • Strong final state interactions for jets • Energy loss of fast quarks/gluons traveling through the plasma jet quenching**Jet Quenching**• Away-side jets vanish • Trigger on a high pT hadron and look for associated hadron as a function of relative azimuthal angle and rapidity The away side jet is absorbed in the medium**z**y x Elliptic Flow • Finite impact parameter b > 0: • Spatial anisotropy in the initial state • Momentum anisotropy in the final state • coordinate space momentum space Infer equation of state of the system?**z**y x Elliptic Flow • Nonzero impact parameter b > 0: • Spatial anisotropy in the initial state • Momentum anisotropy in the final state • coordinate space momentum space • Fourier analysis => v2 = elliptic flow**PHENIX preliminary**PHENIX preliminary How special is this matter? CERES Results are strikingly similar for V2 decreases by ~ 50% from RHIC to SPS Significantly larger pressure (gradients) developed at RHIC**Anisotropic expansion of a**Bose-Einstein condensate**Numerical Hydrodynamics**(Huovinen, Kolb, Heinz, Hirano, Teaney, Shuryak, Hama, Morita, Nonaka, Bass) Assume thermalization between 0.15 and 1 fm/c. Agreement provides strong indication for early thermalization and collective flow.**Big Theoretical Motivation!**Kovtun, Son, Starinets PRL 94, 111601 (2005) Viscosity in Strongly Interacting Quantum Field Theories from Black Hole Physics Using the Kuboformula the low energy absorption cross section for gravitons on black holes, and the black hole entropy formula they found that and conjectured that this is a universal lower bound.**Atomic and Molecular Systems**In classical transport theory and so that as the density and/or cross section is reduced (dilute gas limit) the ratio gets larger. In a liquid the particles are strongly correlated. Momentum transport can be thought of as being carried by voids instead of by particles (Enskog) and the ratio gets larger.**Helium**NIST data**2D Yukawa Systems**in the Liquid State Applications to dusty-plasmas and many other 2D condensed matter systems. Liu & Goree**QCD**• Chiral perturbation theory at low T (Prakash et al.): grows with decreasing T. • Quark-gluon plasma at high T (Arnold, Moore, Yaffe): grows with increasing T.**QCD**Low T (Prakash et al.) using experimental data for 2-body interactions. High T (Yaffe et al.) using perturbative QCD. η/s≈1/2 just above Tc from lattice (Nakamura, Sakai) and classical quasiparticle model (Gelman, Shuryak, Zahed)**Relativistic Dissipative Fluid Dynamics**In the Landau-Lifshitz approach u is the velocity of energy transport.**Extracting η/s from RHIC/LHC data**• Elliptic flow • Hanbury Brown & Twiss interferometry • Momentum spectra • Momentum fluctuations • Photon & dilepton spectra • Jet quenching**Dependence of v2 on viscosity.**Romatschke & Romatschke 2007/2008**3-particle correlations - is there a Mach cone?**Is QGP physics at RHIC and SPS the same or different?**gT**gL (z - ut) The Mach cone generated by a high energy parton in the plasma Asakaw, Mueller, Neufeld, Nonaka, Ruppert Energy density Momentum density**An approach to model**the collisions from first impact until the last hadronic scattering. Duke (Bass, Muller) Nagoya (Nonaka) Texas A&M (Fries)Iowa (Li) Minnesota (Kapusta)**Theory Outline**1. Hard parton scattering and jet production. 2. Generation of classical gluon field by large momentum partons that have not scattered (color glass condensate). 3. Decay of classical gluon fields via particle production. 4. Matching to relativistic viscous fluid dynamics in 3+1 dimensions. 5. Phase transition or crossover from quarks and gluons to hadrons. 6. Rescattering of hadrons followed by freestreaming to the detectors.**Color Glass**• Start from a large nucleus. • How does it look in the limit p+ and Bjorken-x << 1? • Gluon density reaches saturation • Gluon density sets a scale • High density limit of QCD (Mueller & Qiu, McLerran & Venugopalan, Weigert, McLerran & Kovner, …) • Large number of gluons in the wave function: classical description of the gluon field**Color Glass: Two Nuclei**• Gauge potential: • In sectors 1 and 2 single nucleus solutions are valid • In sector 3 (forward light cone): • YM in forward direction: • Set of non-linear differential equations • Boundary conditions given by the fields in the single nuclei Coarse-grain color charges in 2d sheets**Initial Energy Density at RHIC**σ = quarks+antiquarks+(CA/CF)gluons per unit area Q0 = cutoff between IR and UV Qs2=αsσ = saturation scale From IR only**Why LHC?**SPS: 8.6 GeV/nucleon Pb-Pb in cm RHIC: 100 GeV/nucleon Au-Au in cm LHC: 2700 GeV/nucleon Pb-Pb in cm • Jets played no role at SPS, an important role at RHIC, • and will dominate at LHC. • The Z0 will provide a standard candle as reference for • all other hard perturbative processes at LHC. • The much greater volumes, energy densities, temperatures • and lifetimes of produced matter at LHC will provide the • lever arm to infer the equation of state and transport coefficients • which is necessary due to the space-time expansion of the system.**Conclusion**• RHIC/LHC are thermometers (hadron ratios, photon and lepton pair production) • RHIC/LHC are barometers (elliptic flow, transverse flow) • RHIC/LHC are viscometers (deviations from ideal fluid flow) • There is plenty of work for theorists (and experimentalists)!**1. Review of quantum statistical mechanics**2. Functional integral representation of the partition function 3. Interactions and diagrammatic techniques 4. Renormalization 5. Quantum electrodynamics 6. Linear response theory 7. Spontaneous symmetry breaking and restoration 8. Quantum chromodynamics Resummation and hard thermal loops Lattice gauge theory Dense nuclear matter Hot hadronic matter Nucleation theory Heavy ion collisions Weak interactions Astrophysics and cosmology Conclusion Appendix Finite-Temperature Field TheoryPrinciples and ApplicationsJoseph Kapusta and Charles Gale